UCC2818A: How does the PFC compare to the PFC in the UCC28513?

I am designing a PFC for a 400Hz application. A colleague of mine successfully designed a good PFC that drove a Flyback using the UCC28513. I am weighing my options between the 28513 and 2818A. My question pertains only to the PFC portion of the 28513. As far as I can tell the biggest difference is that the 2818A has a soft-start feature for the PFC, which is something I do like. But I am curious how the two compare in terms of THD performance and power factor for a given application.